Process of tanning



N'Mdef-) MILLOOHAU sur. CHAILLY.

PROCESS 0F AND APPARATUS FOR TANNING'. No. 375,455.

Patented Deo. 27, 1887.

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if UNITED STATES- PATENT OFFICE.

ADOLPHE MILLOCHAUVAND FRANQOIS CHAILLY, OF PARIS, FRANCE, AS-

SIGNORS TO CAMILLE AUGUSTE MILLET, OF SAME PLACE.

PROCESS OF TANNING.

SPECIFICATION forming part of Letters Patent No. 375,455, dated December 27, 1887.

Application filed November 30, 1856. Serial No. 220,271. (No model.) Patented in France Juno 23, 18S6,I\'o.176,965; in Belgium October 7, 1886, No. 751,770; in Austria -Hungary November 5, 1886, No. 44,360, and in England November 22, 1886, No.

`To all whom t may concern.-

Beit known thatJ we, ADOLPHE MILLOCHAU and FRANoIs CHAILLY', both citizens of the Republic of France, and residents of Paris,

France, have invented a new and useful Improvement in Processes of Tanning, (for which we have obtained patents in France, dated June 23, 1886, No. 176,965; Belgium, dated October 7, 1886, No. 74,7 70; AustriaeHungary,

io dated November 5, 1886, No. 44,360, and Great Britain, dated November 22,1886, No. 15,200,)

of which the, following is a full, clear, and ex act specification. y

' Our invention hasfor its chief object to enable the tanning of hides and skins to be ef-l fected more rapidly than heretofore.

The'n'vention consists in withdrawing or sucking out, by means of a ventilator, rotary pump, or other apparatus, the air found at the 2o top of a closed tanning-vat containing the skins and tanning-liquid, and conducting said air back again to the bottom'of the tanningvat by means of the same apparatus which has Withdrawn the air from the top 'of the vat. 2 5 The invention also consists in mixing with rthe air withdrawn from the top of the tanning-vat a` small quantity -of atmospheric air taken from the outside ofthe apparatus.

Oursaid invention is illustrated in the accompanying drawings, in which Figure 1 is a plan View showingthe arrangement of apparatus for carrying our process into practice, and Fig. 2 is a central vertical section of thesaid apparatus.

The hidcs or skins to be tanned are suspended from bars D, placed at the upper part of the tan-pit E, which can be hermetically closed by means of a hinged cover, G, or a hydraulic joint, or by any other suitable A rotary pump or fan, B,'forces air through the pipe A to the bottom of the tanpit. The air forcedinto the liquid by this pump can be drawn from the pit through the pipe F, so that it is more or less charged with tannic principles. Furthermore, such air, ob- A tained in the described manner, can be mixed with a suitable quantity of air drawn from the external atmosphere through the pipe C in or-f duce water and tannic principles into the pit.

Instead of placi n g the substances from which the tanning-liquor is formed in the pit with the hides or skins, the said tanning-liquor can be prepared separately. For this purpose we place the water and the tanning substances in a vat, which can be closed, if desired, and we introduce a current of air at the bottom of this vat to effect the maceration and dissolution of the bark and tanning. The substances can 4be stirred by the air either in a continuous manner or at intervals. Vhen the liquors are thus prepared, they are poured into the pit in which the hides are suspended as described, and the tanning is thencommenced, air being caused to enter continually at the bottom of the pit.

The tanning-liquors can be prepared either with pulverized bark orwith pieces or chips of wood containing tannic principles.

The liquors can be of any desired degree of concentration.

According to circumstances, we can, as already stated, inject at the bottom of the vat either the air or vapor alone, which is drawn from the upper part of the pit through the pipe F, or air mixed in variable proportions with external air drawn through the pipe C.

The stirring or agitating of the liquor by air, as described, produces excellent results in the tanning, andthe liquors are perfectly clear.

It might have been supposed that the air would give rise to oxidation capable of pro ducing gallic acid, which would have blackeued the hides; butthis result is not produced, the liquors, on the contrary, being puried.

The chief merit or advantage of our process of tanning resides in the fact that a continuous circulation of air charged with tannic principles takes place through a closed vat or pit;

or, in other words, the air which is at first admitted at the bottom of the vat is used over and over again, it being forced to the bottom of the vat and drawn ont at the top thereof by the same apparatus, such as an airpuinp or blower. It will be understood that the circulation of the saine air is continued as many times as may be found necessary for the tanning of different kinds of skins. Since the oxygen is practically extracted from the air after a few passages through the tanningliquor, it follows that the production of gallic acid cannot take place, and hence we avoid the formation of badly-tanned or dark leather. As there is some loss of air by leakage through the joints or walls of the vat and pipes, and it is desirable to prevent the formation of a vacuum, we make provision for the admixture of fresh air with the charged air which has been repeatedly passed through the vat. The means for attaining such end have been fully set forth in the description of the apparatus.

W'e claiml. The process of tanning hides, consisting in placing the tanning-liquor and hides in a closed vat or pit and causing a constant eirculation of the same atmospheric air through such vat by injecting the air at the base of the vat, withdrawing it at the top thereof, and repeatedly conveying the air charged with tannie principles back again to the base of the vat, substantiallyr as described.

2. The process of tanning hides, consisting in placing the tanningliquor and the hides in a closed vat or pit, continuously passing the same atmospheric air through the same by admitting it at the bottom of the vat, withdrawing it at the top of the latter, and admixing the air charged with tannic principles with common atmospheric air and carrying the mixture back again to the bottom ot' the tanning-vat, substantially as described.

In testimony whereof' we have hereunto signed our names in the prucsence of two subscribing witnesses.

ADOLPHE MILLOCHAU. FRANQOIS CHAILLY. Witnesses:

A. PENIssAT, A. GOUDKIND. 

